A principal function of the skin is to retain essential fluids while protecting against harmful intruding agents. Therefore, the skin can be a formidable barrier for delivery of many pharmaceutical agents (e.g., medicaments, drugs, prodrugs, etc.). Many compositions have been described in the literature to enhance the transdermal penetration of certain pharmaceutical agents. Such compositions typically include chemical penetration enhancers such as alkanes, alkenes, alcohols, amides, amines, amine oxides, carboxylic acids, ethers, esters, halocarbons, ketones, and sulfoxides.
Chemical penetration compositions have also been described that, for one purpose or another, involve the use of either lower or higher alcohols, or occasionally both lower and higher alcohols. See, e.g., U.S. Pat. No. 4,752,612 (Saito et al.), and U.S. Pat. No. 5,149,719 (Ferber et al.), and International Publication No. WO 93/07903 (Deckner). Penetration enhancing compositions involving the use of both lower and higher alcohols in an aqueous system (i.e., hydroalcoholic systems) are described (see, e.g., U.S. Pat. No. 4,006,218 (Sipos)); however, such systems can be quite irritating and often include additional penentration enhancers that increase this irritation. Thus, there is still a need for hydroalcoholic compositions containing a pharmaceutical agent that delivers the pharmaceutical agent transdermally.